KR20030041083A - Rotor platform modification and methods using brush seals in diaphragm packing area of steam turbines to eliminate rotor bowing - Google Patents

Abstract

PURPOSE: A steam turbine and a method for eliminating bending of a rotor shaft are provided to eliminate or minimize thermal bending caused by non-uniform heat distribution at the circumference of a rotatable component, resulting from the frictional contact between a brush seal and the rotatable component. CONSTITUTION: A steam turbine comprises a rotatable component(11) including a rotor shaft(12) having a rotor shaft surface; a fixed component(17) about the rotatable component; a brush seal(26) carried by the fixed component for sealing engagement with the rotatable component; at least a pair of wheels(14) on the rotatable component spaced axially from one another. The rotatable component includes a plurality of buckets(16) spaced circumferentially from one another on each of the wheels and a unit for inhibiting non-uniform circumferential heat transfer to the rotor shaft surface due to heat generated by frictional contact between the brush seal and the rotatable component thereby to eliminate or minimize bending of the rotatable component. The inhibiting unit includes an annular platform(40) projecting radially outwardly of the rotor shaft surface at an axial location between the wheels. The brush seal is disposed between the buckets on the wheels and the brush seal engages a sealing surface on the platform radially outwardly of the rotor shaft surface.

Description

ROTOR PLATFORM MODIFICATION AND METHODS USING BRUSH SEALS IN DIAPHRAGM PACKING AREA OF STEAM TURBINES TO ELIMINATE ROTOR BOWING}

The present invention is a stationary component and a rotating configuration, arranged and positioned to eliminate thermal warpage caused by dissipation of heat that is not uniform around the rotating component due to heat generated by frictional contact between the brush seal and the rotating component. It relates to a steam turbine having a brush seal between elements, and more particularly, to an apparatus and a method for removing axial thrust loads in case of thermal warpage as well as breakage of brush seals in such turbines.

U. S. Patent No. 6,168, 377, assigned to the applicant, discloses a steam turbine having a brush seal positioned between a stationary component and a rotating component of the rotor shaft. In particular, an axial flange is provided on the dovetail of the bucket, which bucket dovetail is fixed in a shape complementary to the dovetail of the rotor wheel. The brush seal, which consists of an arc-shaped array of metal bristles projecting from the stationary component towards the rotating component, ie from the flange on the bucket dovetail, has a bristle tip coupled to and supported by the flange surface. As disclosed in US Pat. No. 6,168,377, heat is generated due to the contact between the bristles of the brush seal and the opposing sealing surface, ie the flange.

As disclosed in US Pat. No. 6,168,377, the contact between the brush seal and the sealing surface must be located radially outward of the rotor shaft to separate heat generated from the outer diameter of the rotor. On the other hand, the heat generated by the friction results in an uneven temperature distribution around the circumference of the shaft, resulting in uneven axial expansion of the rotor and consequently the bending of the rotor. Various methods and apparatus are disclosed to eliminate this problem, one of which is to locate the friction generating surface on the bucket dovetail flange radially outward of the shaft outer diameter. In this way, the heat generated is separated from the rotor to eliminate all tendencies of the rotor.

These and other configurations of these patents use conventional labyrinth-type packing seals as preliminary seals for brush seals on the inside of diaphragm webs. These labyrinth seals are located directly adjacent to the outer diameter of the shaft. However, brush seals are sensitive to wear and tear. The brush seal, the brush seal of this patent configuration, must be spaced outward of the shaft break and the sealing diameter is varied from the bucket dovetail platform to the rotor shaft. This in turn reverses the pressure distribution on the shaft and the thrust on the rotor in the axial direction. Thus, rotor dynamic restraint limits the number of stages when brush seals can be used and labyrinth-type sealing teeth are used instead of such seals, and reduces section efficiency due to increased secondary losses. Thus, not only does the problem of thermal warpage of the steam turbine rotor due to uneven heat dissipation caused by contact between the brush seal and the complementary sealing surface is eliminated, but the axial thrust load on the rotor bearing is eliminated in case of brush seal failure. Or there is a need to provide a sealing system for an steam turbine that can be minimized.

According to a preferred embodiment of the present invention, a brush seal is provided that is located radially outward of the outer diameter or surface of the shaft of the rotating component to eliminate thermal warpage of the rotor due to uneven heat dissipation. The brush seal can be applied in combination with a labyrinth seal at substantially the same radial position to eliminate thrust loads in case of breakage of the brush seal. In particular, the platform is formed around the rotor between adjacent axially spaced wheels supporting the turbine bucket, the platform projecting radially outward from the surface of the rotor. In a preferred embodiment, the platform is in the form of an annular pedestal having an axially reduced neck and at least one, preferably a pair of flanges extending axially at the radially outer end of the platform. One or more flanges are actually one or more fins that are axially cantilevered from the neck portion of the pedestal and allow to dissipate heat generated by frictional contact of the brush seal on the platform surface before affecting rotor dynamics. Play a role. Thus, the platform configuration can provide sufficient area and the flanges or fins can dissipate heat locally, mitigating the effects of rotor vibrations, and thus allowing similar brushes to be applied to all steam turbine section stages. do. The cantilever supported flanges or pins are provided radially voids, ie in wheel spaces, between the flanges or pins and the rotor surface, whereby the frictional heat generated by the brush seal contact with the sealing surface of the platform is first axially and It disperses radially before it affects the thermal dynamics of the rotor. This heat dissipation is sufficient to minimize or eliminate the thermal response of the rotor to heat generated by friction.

The diaphragms between adjacent wheels have a web that extends radially inward in the wheel space and not only support the brush seal but also support one, preferably a plurality of labyrinth seal teeth. The labyrinth seal tooth is removed at the tapered edge spaced from the surface of the platform and preferably serves as a preliminary seal of the brush seal. Thus, the labyrinth tooth is preferably located on the downstream side of the brush seal. If the brush seal is broken, the labyrinth tooth will limit performance deterioration. However, the brush seal may be located downstream of the labyrinth seal tooth or in the middle of the labyrinth seal tooth. In addition, since the regions on the upstream and downstream sides of the pedestal exposed to the diaphragm and the integral cavity, ie the wheel space, are not substantially the same, pure axial thrust from the leakage flow through the labyrinth seal is not generated.

In a preferred embodiment according to the invention, a rotary component comprising a rotor shaft having a rotor shaft surface, a stationary component around the rotary component, and the stationary component for sealingly coupling with the rotary component And at least one pair of wheels axially spaced apart from each other on the rotating component, the brush seal supported by the wheel component, the rotating component comprising a plurality of buckets circumferentially spaced apart from each other on the respective wheels; Means for removing or minimizing warpage of the rotating component by preventing uneven circumferential heat transfer to the rotor shaft surface due to heat generated by frictional contact between the brush seal and the rotating component; The prevention means comprises an annular platform projecting radially outwardly of the rotor shaft surface at an axial position between the wheels, the brush seal disposed between the buckets on the wheel and radially of the rotor shaft surface. A steam turbine is provided that engages the sealing surface on the platform outward.

In another preferred embodiment according to the invention, a brush component is provided for sealingly engaging a rotary component comprising a rotor shaft having a rotor shaft surface and a rotary component along a vapor leakage flow path about the rotary component. In a steam turbine having a stationary component, the rotor shaft deflects due to heat generated by frictional contact between the brush seal and the rotating component resulting in circumferential uneven distribution of heat around the rotating component. A method of substantially removing the frictional contact area along a sealing surface spaced radially outwardly of the rotor shaft surface between the rotating component and the brush seal and between the sealing surface and the rotor shaft surface. By aligning with the rotor shaft surface, The rotating component and removing the brush rotor comprising a heat step to prevent the circumferential direction could not uniform due to heat transfer to the rotation component caused by frictional contact between the seal shaft deflection method is provided.

1 is a schematic cross-sectional view of a portion of a steam turbine showing the turbine bucket and diaphragm disposed along the turbine shaft and the position of the combined brush / labyrinth seal;

FIG. 2 is an enlarged partial cross sectional view showing a combined brush and labyrinth that engage a radially projecting platform in wheel space between adjacent buckets. FIG.

<Explanation of symbols for main parts of drawing>

10 steam turbine 11 rotating component

12: shaft 14: wheel

16 bucket 17 fixed component

18 nozzle part 22 diaphragm inner web

24: outer surface 26: brush seal

28: metal bristle 34: annular groove

38: tip 40: platform

42: base 44: neck portion

46: fin 48: wheel space

60: labyrinth seal teeth

Referring now to FIG. 1, a steam turbine having a rotating component 11, for example a rotor or shaft 12, for mounting a plurality of axially spaced wheels 14 for mounting a bucket 16. 10 is shown. A series of nozzle portions 18 are interposed between the buckets and form the vapor flow paths indicated by arrows 20 together with the buckets 16. The partition wall is attached to the diaphragm inner web 22 extending between the wheels 14 of the stage of the turbine, the web and the partition wall forming a fixed component 17 as a whole. It is apparent that the rotor 12 is a continuous elongated single piece metal.

As mentioned above, brush seals have been used at various locations along the rotor, ie between stationary and rotating components in the steam turbine to form a seal. According to a preferred embodiment of the invention, the brush seal is provided between the stationary component 17 and the rotary component 11 respectively at a position radially outward of the outer surface 24 of the rotor 12, such that the brush seal is provided. And uneven heat deformation around the rotor due to frictional contact between the tips of the bristles of the rotor. The brush seal seals from the vapor flow path 20 along the leak flow path as indicated by arrow 19 in FIG. 2. The brush seal may be a conventional structure. For example, as shown in FIG. 2, the brush seal 26 includes a plurality of metal bristles 28 disposed between a pair of plates 30, 32 circumferentially extending about the rotor. desirable. In a preferred embodiment of the invention the brush seal 26 is positioned and supported in an annular groove 34 formed in the web 22 along its upstream portion, ie upstream with respect to the direction of the leaky vapor flow path 19. do. The bristle 28 of the brush seal extends at a cant angle with respect to the radius of the rotor about its axis of rotation and has a tip 38 coupled to the rotating component that together forms the seal.

In order to prevent non-uniform thermal deformation around the rotor due to frictional contact between the tip 38 of the bristles 28 and the sealing surface of the rotating component, the rotor 12 is radial to the rotor surface 24. An outwardly projecting platform 40 is mounted between adjacent wheels 14 of the various rotor stages. In particular, the platform 40 has a radially extending annular pedestal 42 having a neck 44 and at least one, preferably a pair of axially extending annular flanges or fins 46. It may also include (pedestal). In particular, as shown in FIG. 2, the flange or pin 46 is cantilevered axially from the reduced neck portion 44, thus radially and part of the wheel space 48 between the wheels 14. Is matched by. The outer surface of the platform 40 and in particular the upstream outer annular surface 50 radially coincident with the tip of the bristle 28 act as a contact sealing surface with the bristle tip 38. Thus, the contact surface between the tip 38 of the bristles 28 and the rotating component that is heat generated by the frictional contact is located away from the rotor surface 24 in both axial and radial directions. Thus, the heat generated by this frictional contact is first distributed axially towards the central portion of the platform and then radially inwards along the neck 44 of the platform 40. That is, the platform is configured to disperse heat locally and has sufficient area to disperse heat, thereby minimizing all thermal reactions of the rotor to thermal effects resulting from brush seal contact with the sealing surface of the platform 40. Or remove it.

In addition, one or more labyrinth seal teeth 60 are supported by the web 22 in one or more annular arrays around the platform 40. The labyrinth tooth 60 is tapered along its radially inner edge and spaced at a minimum distance from the surface of the platform 40 to perform a labyrinth shaped seal, ie any other vapor exiting through the brush seal. Provides a sinuous path for leakage flow. Preferably, the labyrinth tooth is located downstream of all leaking flow through the brush seal and acts as a preliminary seal for the brush seal. Since the brush seal and labyrinth seal are located on substantially the same diameter, the axial rotor thrust resulting from the breakage of the brush seal is substantially eliminated.

Although the invention has been described in terms of the most practical preferred embodiments, it is intended that the invention not be limited to the disclosed embodiment but rather include various modifications and equivalent arrangements included within the spirit and scope of the appended claims. .

According to the present invention, a brush seal is provided that is located radially outside of the outer diameter or surface of the shaft of the rotating component to eliminate thermal warpage of the rotor due to uneven heat dissipation, the brush seal being substantially at the same radial position. It can be applied in combination with the labyrinth seal, which has the effect of removing the thrust load in case of breakage of the brush seal.

Claims (10)

In the steam turbine, A rotary component 11 comprising a rotor shaft 12 having a rotor shaft surface, A stationary component 17 around the rotating component, A brush seal 26 supported by the stationary component for sealingly engaging the rotating component; At least one pair of wheels 14 axially spaced apart from each other on the rotational component, the rotational component comprising a plurality of buckets 16 circumferentially spaced from each other on the respective wheels. and, Means 40, 46 for preventing or minimizing warpage of the rotating component by preventing uneven circumferential heat transfer to the rotor shaft surface due to heat generated by frictional contact between the brush seal and the rotating component. Includes; The prevention means comprise an annular platform 40 projecting radially outward of the rotor shaft surface in an axial position between the wheels, The brush seal is disposed between the buckets on the wheel and engages a sealing surface on the platform radially outward of the rotor shaft surface. Steam turbine. The method of claim 1, A labyrinth seal tooth 60 extending between the stationary component and the platform and axially spaced from the brush seal. Steam turbine. The method of claim 2, The rotating component and the fixed component define a vapor leakage flow path 19 therebetween, wherein the brush seal is located upstream of the labyrinth tooth in the leakage flow path. Steam turbine. The method of claim 1, The platform includes an annular extending pedestal 42 having a neck 44 and at least one flange 46 extending axially from the neck toward one of the wheels, the sealing surface of the platform Located on the flange Steam turbine. The method of claim 4, wherein A labyrinth seal tooth 60 extending between the stationary component and the platform and axially spaced apart from the brush seal, wherein the platform and the stationary component define a vapor leak flow path 19 therebetween. And the brush seal is located upstream of the labyrinth tooth in the vapor leakage flow path. Steam turbine. The method of claim 4, wherein The securing component has a diaphragm with an inner web 22 radially spaced outwardly and radially coincident with the platform, the brush seal extending from the web and sealing surface 50 on the platform. Combined with Steam turbine. The method of claim 6, A labyrinth tooth 60 extending from the web terminating at a tooth tip radially spaced from the platform, the labyrinth tooth axially spaced from the brush seal, the rotating component and The fixed component defines a vapor leakage flow path therebetween, wherein the brush seal is located upstream of the labyrinth tooth in the vapor leakage flow path. Steam turbine. The method of claim 7, wherein The platform has a neck portion 44 and at least one flange 46 extending axially towards one of the wheels and the neck portion, the sealing surface being located on the flange. Steam turbine. The method of claim 1, The platform includes a pedestal 42 extending annularly around the rotational component, the pedestal extending radially from the neck portion 42, each of which extends in an opposite axial direction from the wheel towards the wheel. A pair of flanges 46, the annular surface 50 being positioned on one of the flanges Steam turbine. A rotation component comprising a rotor shaft 12 having a rotor shaft surface, and a fixing for supporting the brush seal 26 to sealally engage the rotation component along the vapor leakage flow path 19 around the rotation component. In the steam turbine with component 17, the heat generated by the frictional contact between the brush seal and the rotating component causes the rotation of the rotor shaft to be caused by circumferentially uneven distribution of heat around the rotating component. In a method for substantially removing warpage, A portion of the wheel space 48 between the rotating component and the brush seal and between the sealing surface and the rotor shaft surface along the sealing surface 50 spaced radially outward of the rotor shaft surface is located in the rotor shaft. Positioning in conformity with the surface to prevent circumferential uneven heat transfer to the rotating component due to heat generated by the frictional contact between the rotating component and the brush seal. How to remove rotor shaft warpage.